# PCAT Biological Processes – Retrograde Action Potentials

• by
• Jan 03, 2018
• PCAT Question of the Day

Retrograde action potentials are prevented by:

A) leaky K+ diffusion out of the cell

B) absolute refractory period of voltage-gated Na+ channels

C) Na+/K+ ATPase

D) temporal summation of signals from dendrites

##### Click for Explanation

Retrograde action potentials are prevented by the absolute refractory period of voltage-gated Na+ channels. Since recently opened Na+ channels cannot reopen, the action potential is prevented from traveling in a retrograde fashion. It can only progress anterograde down the axon. If you ever see retrograde conduction mentioned in a neuron question of the MCAT, you should be suspicious of a trap answer.

A) leaky K+ diffusion out of the cell, incorrect, K+ diffusion contributes to the resting potential and has little to do with the action potential.

B) absolute refractory period of voltage-gated Na+ channels, correct.

C) Na+/K+ ATPase, incorrect, The Na+/K+ ATPase helps establish the concentration gradient of Na+ and K+ in the neuron.

D) temporal summation of signals from dendrites, incorrect, Temporal summation of signals from dendrites contributes to action potentials and has nothing to do with anterograde signal conduction.